Simulation of heat treatment for heads

[DOKKU AJAY]

Dear All,

 

Requested to feed in your comments.

 

Design code is ASME Sec.VIII Div.1.

Material: SA 516 Gr.70N

Thk (Nom):16mm after forming.

No heat treatment of the equipment.

 

We have a situation here wherein heads for vessels after cold forming have to be normalized, as per client specs. The plates (from stock) from whcih heads will be formed is already in normalized condition. No additonal simulation test results are reported in the MTC.

 

As per, UCS 85 (c), material used in the vessel shall be represented by test specimens which have been subjected to the same heat treatments above the lower transformation temperature and post weld heat treament.....

 

My understanding to the clause is, the test coupons from the same heat and plate no. shall be normalized along with the heads (by the froming vendor) to simulate the heating / cooling conditions and then shall be tested for mechanical properties (Tensile/Yield/Elongation) as per ASME Sec.II A requirement.

 

Please confirm. Kindly also let me know, if any other precaution has to be taken.

 

 

Dokku Ajay Kumar
Mobile: +966 500071054

[Bathula Raghuram (Mumbai - PIPING)]

your understanding is correct, you can simulate test coupon along with post forming heat treatment of dished end and test it. Generally it is requested from mill to get guaranteed results from the mill itself.

[Chaitanya Purohit]

Dear Ajay,

As a good engineering practice its good to have simulation test coupon heat treated with the Head and tested so that you can ensure that the mechanical properties are met.

But in my opinion simulation of normalizing is not mandatory.....

UCS 85(c) is not clear about upper critical temperature and hence I suggest you to seek Interpretation from ASME or look for some interpretation if readily available.

In my opinion Normalizing on head will reinstate the properties (similar to the supplied condition, i.e. Normalizing) which might have deteriorated during cold forming. Hence simulation of Normalizing is not required.  Situation would be different if your supplied condition of plate would be "as rolled" (i.e without Normalizing).

Mechanical properties will not change even for n numbers of normalizing. Chances of change in Mechanical properties will only in case of accelerated cooling.
 
More comments to have better clarity from other members are highly appreciated.  

Regards.
CK

[DOKKU AJAY]

I had a similar thought & I agree to you some extent, however, the other thing which came in to my mind is the the temperature range at which the head is getting normalized.

 

I believe that normalizing of heads can't exactly simulate the conditions through which the plates had undergone i.e temp. band withing which the plates were normalized. Also the cooiling conditions in the MTC only indicates in air. Moreover the holding time may also play a vital role. I believe,This may lead to change in the properties to some extent. (Metallurgist expertise in this regard would be beneficial for the group)

 

Code is very clear that simulation is to be done for heat treatment above the lower transformation temperature & PWHT. Hence, i believe there is no need to look into interpretation.

 

Generally, normalizing is to done minimum 100 deg.cent above the upper critical tempearature based on I-C diagram wherin the material goes into austenitic stage. Should there be an upper limit to the normalizing temperature??

 

I would like to add one more query in this regard, for which there could be a written interpretaion. If yes, then please share :

 

"UCS85(C): As per, UCS 85 (c), material used in the vessel shall be represented by test specimens which have been subjected to the same heat treatments above the lower transformation temperature and post weld heat treament..."

 

Query: Same heat treatments : Is there any restriction/limitation on temp.band??

 

 If no, does it effect the mechanical properties?? 
 

Ajay

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From: Chaitanya Purohit <chaitany...@yahoo.co.in>
To: material...@googlegroups.com
Sent: Mon, October 4, 2010 3:20:34 PM
Subject: Re: [MW:7357] Simulation of heat treatment for heads

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[jignes...@linde-le.com]

Dear Mr. Ajay / Mr. Purohit,

I like to share my views on the subject of simulation heat treatment for heads. The discussion is very much limited to P No. 1 only.

Client requirement and code requirement are two separate entity and should not cross referred to reach to final conclusion.

Code Requirements : ( ASME Section VIII Div. 1)

UCS - 85 is very clear about the heat treatment and subsequent testing of test coupon.( inclusion, exclusion both). For our case, as per UCS - 85 (i) no separate testing is required, if heads are normalized and the normalizing temperature is at least  as high as normalising temperature of plate at mill. The exact word in code is-  fully austenizing the material.

But the catch is word - Temperature. In my opinion, it should be similar heat treatment cycle. I need the opinion of members on the issue.

As we do have instances which indicates that variables like soaking time, cooling rate affects the tensile strength of material. ( eg - annealing and normalising of material from same temperature)
Therefore, good fabricators prefer to carry out product testing, once the "Heat Treatment"  crosses upper transformation temperature.

 EN 13445 ( Unfired pressure vessel) calls for the testing of the part, which is cold /  hot formed and subsequently heat treated.

Client Requirements : It is additional requirement other than code and once agreed, to be fulfilled.


With Best Regards,

Jignesh R Rana
Manager - QA & QC

Linde Engineering India Pvt. Ltd.
38, Nutan Bharat Society, Alkapuri, Vadodara 390007, India
Tel.: +91 265 3056789, Fax: +91 265 2335213 , Mobil:  +91 90999 86019
jignes...@linde-le.com, www.linde-india.com

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